When Raffaele Sollecito, an IT undergraduate from a middle-class family, fell for the young American Amanda Knox, it changed his life forever.

Originally from Bari in southern Italy, Sollecito, the son of a respected urologist, first encountered Knox at a concert not long after she arrived in Perugia.

His initial impression of the Seattle-born foreign exchange student was that she was ''interesting''.

The pair quickly started a relationship and acquaintances said the Italian lavished attention on his new girlfriend.

He was always holding her hand and ''always nice to her'', according to Knox and Meredith Kercher's housemate, Filomena Romanelli.

Sollecito himself described the relationship as ''sentimental''.

The couple sometimes smoked marijuana together and Sollecito, whose sister was a police officer, claimed he was smoking the drug and downloading a cartoon at his house on the night Miss Kercher was murdered.

But prosecutors said his DNA was found on the British student's bra strap, which linked him to the crime.

He had, they said, joined Knox and a third person, drug dealer Rudy Guede, in trying to get Miss Kercher to participate in an extreme sex game that night.

He was arrested on November 6 2007 - four days after Miss Kercher's semi-naked body was found in her bedroom.

He and Knox were found guilty in December 2009 of murdering Miss Kercher, with Knox sentenced to 26 years in prison and Sollecito 25.

But, after an 11-month appeal in a Perugia court, both convictions were thrown out in October 2011.

In September last year, he spoke of how his life was "on hold" as he faced the retrial.

"Every tiny little day, it is constantly on my shoulder, because these trials, this kind of situation, has put my life on hold," Mr Sollecito told ITV's Daybreak.

"I cannot find a normal life, a job, a career or something to focus on instead of thinking about the trial, about the documents, about what will happen, about how to pay lawyers, how to pay my bills," he said.

His alibi was thrown into doubt when police chief Filippo Bartolozzi told the court during the original trial that an inspection of his computer showed there had been no activity on it between 9.10pm on November 1 2007 and 5.32am on November 2.

It was some time between these hours that Miss Kercher is thought to have been killed.

Desperate to convince the world that he had played no part in the terrible events that turned his girlfriend's picturesque cottage into a house of horrors, he even intervened to put across his story through the media, writing from prison to a magazine in Bari before his conviction.

''Consider for one moment what it's like to be in my position,'' he implored his readers.

''You meet a girl at a concert, she lives with friends and from that day you go out more and more, you spend untroubled days together... You can't ask for any more from life.

''Then one morning you return to her house and find a big mess.

''The problems begin: the police arrive, break down the locked door of a bedroom and discover the lifeless body of one of her friends.

''From then on they suspect everyone and everything, including you.

''And you, thinking you are helping them, fall into a trap you have made with your own hands.''